The present invention relates to a process for preparing a polyaromatic compound comprising a concatenation of two aromatic cycles and carrying at least one amino group on one of the aromatic cycles.
In particular, the invention relates to a biphenyl type compound, one of the benzene cycles of which carries an amino group.
In the present disclosure of the invention, the term xe2x80x9cpolycyclic aromatic compound carrying an amino groupxe2x80x9d means a compound resulting from a concatenation of two aromatic cycles wherein one of the hydrogen atoms of one of the aromatic cycles being replaced by an NH2 group.
The term xe2x80x9caromatic compoundxe2x80x9d means the conventional notion of aromaticity as defined in the literature, in particular by Jerry MARCH, Advanced Organic Chemistry, 4th Edition, John Wiley and Sons, 1992, pp. 40 ff.
For simplicity, the expression xe2x80x9carylxe2x80x9d designates all aromatic compounds, whether they are carbocyclic aromatic compounds or heterocyclic aromatic compounds.
Biphenyl type structures are encountered in many molecules used in the pharmaceutical field. In particular, a process for preparing compounds of the N-(biaryl)-amine type, in particular N-(biphenyl)-amine is sought.
Michael Hird et al. (Synlett 1999, No. 4, 438-440) have described the preparation of such compounds using a coupling reaction between an arylboronic acid and a halogenoaniline, in the presence of a palladium catalyst complexed with a triphenylphosphine, sodium carbonate, dimethoxyethane and water. That publication mentions that the coupling reaction is accompanied by very substantial deamination of the reactant and of the product formed.
A. D. Hamilton et al. [Journal of Medicinal Chemistry 1996, 39, p. 217-223] recommend coupling a 3-methylphenylarylboronic acid with 4-bromonitrobenzene to produce a nitrobiphenyl. It is then necessary to reduce the nitro group to an amino group using hydrogen in the presence of palladium on charcoal.
D. Badone et al., J. Org. Chem 1997, 62, 7170-7173 have proposed coupling an arylboronic acid with a halogenoaniline, where the amino group is protected by an acetyl group. After the coupling reaction, liberation of the amino group involves a supplemental acid treatment step.
Thus, the provision of a process that can effect direct coupling between an arylamine and an arylboronic acid is desirable.
We have now discovered, and this constitutes the subject matter of the present invention, a process for preparing a polycyclic aromatic compound comprising at least one concatenation of two aromatic cycles and carrying at least one amino group on one of the aromatic cycles, characterized in that it consists of reacting an aromatic compound carrying at least one amino group and a leaving group with an arylboronic acid and/or its derivatives in an aqueous medium and in the presence of an effective quantity of a palladium catalyst.
In accordance with the process of the invention, an aromatic compound carrying at least one amino group and a leaving group is reacted with an arylboronic acid: the reaction takes place in an aqueous medium and in the presence of a palladium catalyst to produce a biphenyl carrying an amino group. This latter is obtained without deamination, which is surprising in view of the descriptions in the literature.
More precisely, the aromatic compound carrying at least one amino group and a leaving group, hereinafter designated an xe2x80x9caminoaromatic compoundxe2x80x9d has general formula (I): 
in which:
A designates the residue of a cycle forming all or a portion of an aromatic, monocyclic or polycyclic, carbocyclic or heterocyclic system;
R, which can be identical or different, represents the substituents on the cycle;
Y represents a leaving group, preferably a halogen atom or a sulphonic ester group with formula-OSO2-R, where R is a hydrocarbon group;
n represents the number of substituents on the cycle.
In the formula for the sulphonic ester, R is a hydrocarbon group of any nature containing 1 to 20 carbon atoms. However, given that Y is a leaving group, it is economically advantageous for R to be simple in nature, and more particularly it represents a linear or branched alkyl group containing 1 to 4 carbon atoms, preferably a methyl or ethyl group, but it can also represent, for example, a phenyl or tolyl group or a trifluoromethyl group. A preferred group Y is the triflate group, corresponding to a group R representing a trifluoromethyl group.
Preferred leaving groups are a bromnine or chlorine atom.
The invention is applicable to aminoaromatic compounds with formula (I) in which A is the residue of a cyclic compound preferably containing at least 4 atoms in the cycle, preferably 5 or 6, optionally substituted, and representing at least one of the following cycles:
an aromatic, monocyclic or polycyclic carbocycle;
an aromatic, monocyclic or polycyclic heterocycle containing at least one of heteroatoms O, N or S.
More precisely, and without limiting the scope of the invention, optionally substituted residue A can represent the residue:
1xc2x0 of an aromatic, monocyclic or polycyclic carbocyclic compound.
The term xe2x80x9cpolycyclic carbocyclic compoundxe2x80x9d means:
a compound constituted by at least 2 aromatic carbocycles and forming ortho- or ortho- and peri-condensed systems between them;
a compound constituted by at least 2 carbocycles only one of which is aromatic and forming ortho- or ortho- and peri-condensed systems between them;
2xc2x0 of an aromatic, monocyclic or polycyclic heterocyclic compound.
The term xe2x80x9cpolycyclic heterocyclic compoundxe2x80x9d means:
a compound constituted by at least 2 heterocycles containing at least one heteroatom in each cycle wherein at least one of two cycles is aromatic and forming ortho- or ortho- and peri-condensed systems between them;
a compound constituted by at least one carbocycle and at least one heterocycle wherein at least one of the cycles is aromatic and forming ortho- or ortho- and peri-condensed systems between them.
More particularly, optionally substituted residue A represents one of the following cycles:
an aromatic carbocycle: 
an aromatic bicycle comprising two aromatic carbocycles: 
a partially aromatic bicycle comprising two carbocycles one of which is aromatic: 
an aromatic heterocycle: 
an aromatic bicycle comprising an aromatic carbocycle and an aromatic heterocycle: 
a partially aromatic bicycle comprising an aromatic carbocycle and a heterocycle: 
an aromatic bicycle comprising two aromatic heterocycles: 
a partially aromatic bicycle comprising a carbocycle and an aromatic heterocycle: 
a tricycle comprising at least one carbocycle or an aromatic heterocycle: 
In the process of the invention, an aminoaromatic compound with formula (I) is preferably used in which A represents an aromatic ring, preferably a benzene or naphthalene ring.
The aromatic compound with formula (I) can carry one or more substituents. The substituent can be of any type provided that it does not interfere with the reaction.
The number of substituents present on a cycle depends on the carbon condensation of the cycle and on the presence or absence of unsaturated bonds on the cycle.
The maximum number of substituents that can be carried by a cycle can readily be determined by the skilled person.
In the present text, the term xe2x80x9cpluralityxe2x80x9d generally means less than 4 substituents on an aromatic ring.
Examples of substituents are given below, but this list is not limiting in nature.
Groups R, which may be identical or different, preferably represent one of the following substituents:
a linear or branched alkyl group containing 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl or tert-butyl;
a linear or branched alkenyl or alkynyl group containing 2 to 6 carbon atoms, preferably 2 to 4 carbon atoms, such as vinyl or allyl;
a linear or branched alkoxy group containing 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, such as methoxy, ethoxy, propoxy, isopropoxy, butoxy groups, an alkenyloxy group, preferably an allyloxy group, or a phenoxy group;
a cyclohexyl, phenyl or benzyl group;
an acyl group containing 2 to 6 carbon atoms;
a group with formula:
xe2x80x94R1xe2x80x94OH
xe2x80x94R1xe2x80x94SH
xe2x80x94R1xe2x80x94COOR2 
xe2x80x94R1xe2x80x94COxe2x80x94R2 
xe2x80x94R1xe2x80x94CHO
xe2x80x94R1xe2x80x94Nxe2x95x90Cxe2x95x90O
xe2x80x94R1xe2x80x94Nxe2x95x90Cxe2x95x90S
xe2x80x94R1xe2x80x94NO2 
xe2x80x94R1xe2x80x94CN
xe2x80x94R1xe2x80x94N(R2)2 
xe2x80x94R1xe2x80x94COxe2x80x94N(R2)2 
xe2x80x94R1xe2x80x94SO3M
xe2x80x94R1xe2x80x94SO2M
xe2x80x94R1xe2x80x94X
xe2x80x94R1xe2x80x94CF3 
in which formulae, R1 represents a covalent bond or a linear or branched, saturated or unsaturated divalent hydrocarbon group containing 1 to 6 carbon atoms, such as methylene, ethylene, propylene, isopropylene, isopropylidene; groups R2, which may be identical or different, represent a hydrogen atom or a linear or branched alkyl group containing 1 to 6 carbon atoms or a phenyl group; M represents a hydrogen atom, an alkali metal, preferably sodium, or a group R2; and X represents a halogen atom, preferably a chlorine, bromine or fluorine atom.
More particularly, the present invention is applicable to aminoaromatic compounds with formula (I) in which group or groups R represent:
a linear or branched alkyl group containing 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl or tert-butyl;
a linear or branched alkenyl group containing 2 to 6 carbon atoms, preferably 2 to 4 carbon atoms, such as vinyl or allyl;
a linear or branched alkoxy group containing 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, such as methoxy, ethoxy, propoxy, isopropoxy, butoxy groups, an alkenyloxy group, preferably an allyloxy group, or a phenoxy group;
a group with formula:
xe2x80x94R1xe2x80x94OH
xe2x80x94R1xe2x80x94N(R2)2 
xe2x80x94R1xe2x80x94SO3M
in which formulae, R1 represents a covalent bond or a linear or branched, saturated or unsaturated divalent hydrocarbon group containing 1 to 6 carbon atoms, such as methylene, ethylene, propylene, isopropylene, isopropylidene; groups R2, which may be identical or different, represent a hydrogen atom or a linear or branched alkyl group containing 1 to 6 carbon atoms or a phenyl group; M represents a hydrogen atom or a sodium atom.
More preferably, R represents a linear or branched alkyl group containing 1 to 4 carbon atoms, more particularly a methyl group.
In formula (I), n is a number of 4 or less, preferably 1 or 2.
Examples of compounds with formula (I) that can be cited are 4-bromoaniline, 4-bromo-3-methylaniline, 1-amino-3-bromonaphthalene and 2-chloro-3-aminopyridine.
In accordance with the invention, the aminoaromatic compound with formula (I) reacts with an arylboronic acid with formula: 
in which:
R3 represents an aromatic, monocyclic or polycyclic carbocyclic or heterocyclic group;
Q1, Q2, which may be identical or different, represent a hydrogen atom, a linear or branched, saturated or unsaturated, aliphatic group containing 1 to 20 carbon atoms, or a group R3;
or Q1 and Q2 can be connected together via an alkylene or alkylenedioxy group containing 1 to 4 carbon atoms;
or Q1 and Q2 can be connected together via xe2x80x94Oxe2x80x94Bxe2x80x94Oxe2x80x94 to form a boroxine group with formula (III) in which R3 has the meaning given above: 
More precisely, the arylboronic acid has formula (II) or (III) in which group R3 represents an aromatic carbocyclic or heterocyclic group. R3 can take the meanings given above for A. However, more particularly, R3 represents a carbocyclic group such as a phenyl, naphthyl or heterocyclic group such as a pyrrolyl, pyridyl, pyrimidinyl, pyridazinyl, pyrazinyl, 1,3-thiazolyl, 1,3,4-thiadiazolyl or thienyl group.
The aromatic cycle can also be substituted. The number of substituents is generally at most 4 per cycle but is usually equal to 1 or 2. Reference should be made to the definition of R for examples of substituents.
Preferred substituents are alkyl or alkoxy groups containing 1 to 4 carbon atoms, an amino group, a nitro group, a cyano group, a halogen atom or a trifluoromethyl group.
Regarding Q1 and Q2, which can be identical or different, they more particularly represent a hydrogen atom or a linear or branched acyclic aliphatic group containing 1 to 20 carbon atoms, which may be saturated or comprising one or a plurality of unsaturated bonds in their chain, preferably 1 to 3 unsaturated bonds, preferably simple or conjugated double bonds.
Q1, Q2 preferably represent an alkyl group containing 1 to 10 carbon atoms, preferably 1 to 4, or an alkenyl group containing 2 to 10 carbon atoms, preferably a vinyl or 1-methylvinyl group;
Q1, Q2 can take the meanings given for R3, and in particular any cycle can also carry a substituent as described above.
R3 preferably represents a phenyl group.
The scope of the present invention also encompasses arylboronic acid derivatives such as anhydrides and esters, and more particularly alkyl esters containing 1 to 4 carbon atoms.
Examples of arylboronic acids that can be cited are: benzeneboronic acid, 2-thiopheneboronic acid, 3-thiopheneboronic acid, 4-methylbenzeneboronic acid, 3-methylthiophene-2-boronic acid, 3-aminobenzeneboronic acid, 3-aminobenzeneboronic acid hemisulphate, 3-fluorobenzeneboronic acid, 4-fluorobenzeneboronic acid, 2-formylbenzeneboronic acid, 3-formylbenzeneboronic acid, 4-formylbenzeneboronic acid, 2-methoxybenzeneboronic acid, 3-methoxybenzeneboronic acid, 4-methoxybenzeneboronic acid, 4-chlorobenzeneboronic acid, 5-chlorothiphene-2-boronic acid, benzo[b]furane-2-boronic acid, 4-carboxy benzeneboronic acid, 2,4,6-trimethyl benzeneboronic acid, 3-nitrobenzeneboronic acid, 4-(methylthio)benzene boronic acid, 1-naphthaleneboronic acid, 2-naphthaleneboronic acid, 2-methoxy-1-naphthaleneboronic acid, 3-chloro-4-fluorobenzeneboronic acid, 3-acetamidobenzeneboronic acid, 3-trifluoromethylbenzeneboronic acid, 4-trifluoromethylbenzeneboronic acid, 2,4-dichlorobenzeneboronic acid, 3,5-dichlorobenzeneboronic acid, 3,5-bis(trifluoromethyl)benzeneboronic acid, 4,4xe2x80x2-biphenyldiboronic acid, and esters and anhydrides of said acids.
A palladium catalyst is used in the process of the invention.
The palladium can be supplied in the form of a finely divided metal or in the form of an inorganic derivative such as an oxide or a hydroxide. It is possible to use a mineral salt, preferably a nitrate, sulphate, oxysulphate, halide, oxyhalide, silicate or carbonate, or an organic derivative, preferably, a cyanide, oxalate or acetylacetonate; an alcoholate and still more preferably, a methylate or ethylate; or a carboxylate and still more preferably an acetate. Complexes can also be used, in particular chlorine-containing or cyanide-containing complexes of palladium and/or of alkali metals, preferably sodium, potassium or ammonium.
Particular examples of compounds that can be used to prepare the catalysts of the invention that can be cited are:
palladium (0);
palladium (0) dibenzylideneacetone;
palladium (II) bromide;
palladium (II) chloride;
palladium (II) iodide;
palladium (II) cyanide;
hydrated palladium (II) nitrate;
palladium (II) oxide;
dihydrated palladium (II) sulphate;
palladium (II) acetate;
palladium (II) propionate;
palladium (II) butyrate;
palladium (II) benzoate;
palladium (II) acetylacetonate;
ammonium tetrachloropalladate (II);
potassium hexachloropalladate (IV);
palladium (II) tetramine nitrate;
palladium (II) dichlorobis(acetonitrile);
palladium (II) dichlorobis(benzonitrile);
palladium (II) dichloro(1,5-cyclooctadiene);
palladium (II) dichlorodiamine.
If the catalyst is a palladium compound, it can be introduced in the solid form or in an aqueous solution. As an example, palladium chloride, which is preferably selected, can be introduced in the solid form or in solution in an aqueous hydrochloric acid solution (for example 5% or 10%).
The compound in solution can be deposited on a support.
Metallic palladium can also be deposited on a support.
The support is selected so that it is inert under the reaction conditions.
Examples of supports that can be employed are mineral or organic supports such as charcoal, activated charcoal, acetylene black, silica, alumina, clays, and more particularly, montmorillonite or equivalent materials or organic polymers, for example the polyvinyl polymers PVC (polyvinyl chloride) or PVDC (polyvinylidenechloride), or polystyrene polymers that may be functionalised with nitrile functions, or polyacrylic polymers (in particular polyacrylonitrile).
In general, the metal is deposited in an amount of 0.5% to 10%, preferably 1% to 5% by weight of catalyst.
Of the catalysts cited above, the preferred catalyst is palladium chloride, palladium acetate or palladium deposited on charcoal.
The catalyst can be employed in the form of a powder, pellets or granules.
In accordance with the process of the invention, compounds (I) and (II) are reacted in the presence of a base.
The bases used are alkali metal hydroxides, preferably sodium or potassium; alkaline-earth metal hydroxides, preferably calcium; or ammonium hydroxide; alkali metal carbonates or bicarbonates, preferably sodium or potassium carbonate; metal phosphates, preferably sodium or potassium carbonate. It is also possible to use an amine, preferably a secondary or tertiary amine. The following can in particular be cited: diisopropylamine, pyrrolidine, morpholine, triethylamine, triethanolamine, diisopropylamine.
In accordance with the process of the invention, the aminoaromatic compound and arylboronic acid can advantageously be reacted in an aqueous medium in the proportions mentioned below and in the presence of a palladium catalyst and a base.
The quantity of reactants employed is such that the mole ratio of arylboronic acid/aromatic compound is advantageously 1 or more, and is preferably in the range 1 to 1.2.
The quantity of catalyst employed, expressed as the mole ratio of the metal to the arylboronic acid, is between 5xc3x9710xe2x88x927 and 0.2.
The quantity of base employed, expressed as the ratio between the number of moles of OH and the number of moles of arylboronic acid, is preferably between 2 and 4, more particular about 2.
The quantity of water added is such that the medium can be stirred. It is advantageously in the range 10% to 200% by weight of the reaction medium. The water is generally supplied by the base.
The reaction temperature is advantageously in the range from ambient temperature (usually between 15xc2x0 C. and 25xc2x0 C.) to 130xc2x0 C., preferably in the range 50xc2x0 C. to 100xc2x0 C.
Generally, the reaction is carried out under autogenous pressure of the reactants.
In a preferred variation of the process of the invention, the process of the invention is carried out in a controlled atmosphere of inert gases. An atmosphere of rare gases can be established, preferably argon, but it is cheaper to use nitrogen.
From a practical viewpoint, the process is simple to carry out. All of the reactants are charged and heated for the period required for the reaction to be completed.
The polycyclic aromatic compound is recovered conventionally, for example by extraction using an organic solvent; ether-oxides can be cited, preferably isopropyl ether; aliphatic or aromatic hydrocarbons, which may or may not be halogenated, preferably toluene.
A polyaromatic compound is obtained that can be represented by formula (IV): 
in which formula (IV), A, R, R3 and n have the meanings given above.
More particularly, the invention is applicable to preparing 4-phenyl-3-methylaniline.
Non-limiting examples will now be given by way of illustration only.
In the example, a yield (RT) is defined corresponding to the ratio between the number of moles of product formed and the number of moles of substrate transformed.